1. Field of the Invention
The present invention relates to a system for processing fuel vapor generated in a fuel tank mounted on an automotive vehicle, etc.
2. Related Art
It is well known that fuel vapor due to volatilization of fuel, as a result of an increase in temperature, fills a fuel tank mounted on an automotive vehicle, etc., which in turn increases the internal pressure of the fuel tank in the closed state thereof. If the internal pressure of the fuel tank is equal to or greater than a predetermined value, there is a possibility that fuel vapor can flow into an engine making starting of the engine impossible, or leaks from the joints of fuel lines, etc. For this reason, the rise in internal pressure of the fuel tank is suppressed by discharging fuel vapor from the fuel tank. When discharging fuel vapor, fuel vapor is introduced into a device filled with activated carbon or the like, referred to as a vapor canister, in which the fuel vapor is adsorbed by activated carbon or the like, thus resulting in the discharge of purified gas into the atmosphere.
For the continuous use of the vapor canister, a process of adsorbing fuel vapor as well as a process of collecting adsorbed fuel vapor is required. In order to continuously perform the process of adsorbing fuel vapor and the process of collecting adsorbed fuel vapor, a system having a means or device for controlling the processes is required. Thus, various fuel-vapor processing systems have been developed conventionally.
By way of example, Japanese Published Unexamined Patent Application Publication No. 2001-295703 discloses a fuel-vapor recovery device including a canister having an adsorption means for adsorbing fuel vapor introduced from a fuel tank, and a membrane separation module for separating fuel vapor flowing from a discharge port of the canister into an air rich component and a fuel-vapor rich component by a separation membrane having selective air permeability, in which the membrane separation module has a discharge port for the air rich component, which is disposed on the permeable side of the separation membrane and is connected to the induction pipe of the engine so that the membrane separation module is actuated by a membrane separation driving force generated by the negative pressure of the engine, and a discharge port of the fuel-vapor rich component, which is disposed on the nonpermeable side of the separation membrane and is connected to the fuel tank so that a fuel-vapor component contained in the fuel-vapor rich component is liquefied in the fuel tank or absorbed in liquid fuel for recovery.
With this fuel-vapor recovery device, since air containing fuel vapor, generated in the fuel tank or by purging the canister, is separated by the selective air permeability-type membrane separation module using the engine's negative pressure as a membrane separation driving force, no mounting of a vacuum pump is required. Moreover, even if a membrane-permeated component derived from the membrane separation module is introduced into the induction pipe of the engine, no influence is exerted on the components of the discharged gas. Furthermore, even if a large amount of fuel vapor is produced, no fuel vapor is released into the atmosphere.
Japanese Published Unexamined Patent Application Publication No. 2004-132263 discloses an evaporated-fuel processing device for an internal combustion engine, including a canister for adsorbing evaporated fuel generated in a fuel tank, a feed pump for feeding fuel in the fuel tank to the internal combustion engine, a fuel vapor separation unit for separating process gas containing a high concentration of fuel vapor from purge gas purged from the canister, a process-gas passage for circulating process gas to a suction port of the feed pump, a bubble discharge passage for discharging air bubbles led to the suction port of the feed pump, and a temperature reduction unit for reducing the temperature of an outlet of the bubble discharge passage with respect to the temperature of an inlet thereof. With this evaporated-fuel processing device, evaporated fuel can be processed by condensing evaporated fuel generated in the fuel tank, which is then taken into in the feed pump.